1. Field of the Invention
The present invention relates to an improved gear wheel/pawl engagement for a ratcheting tool, e.g., a ring spanner or a combination wrench having a box end.
2. Description of the Related Art
U.S. Pat. No. 3,838,614 to O'Donnell issued on Oct. 1, 1974 discloses a ratcheting tool including a ratchet gear 26 mounted in a box end of a tool handle 1. A compression spring 20 is mounted in an elongated compartment 12 in the web area for biasing a double tooth dog 22 to engage with the ratchet gear 26. The elongated compartment 12 is slanted to provide improved engaging effect between the double tooth dog and the ratchet gear. Yet, manufacture of this slanted, elongated compartment 12 is relatively difficult, and an additional ratchet cover 14 that adversely affects the aesthetically pleasing effect is required.
U.S. Pat. No. 4,991,468 to Lee issued on Feb. 12, 1991 discloses a wrench body including a driver wheel 17 mounted in a head 10 thereof. A spring 18 is mounted in lateral hole 102 in the head 10 for biasing a pawl 40 to engage with the ratchet gear 26. A tiny plate 19 is provided to seal the hole 102 and to which an end of the spring 18 is attached. Nevertheless, it is difficult to control the position of the tiny plate 19 that affects the biasing force of the spring 18. In some cases, the driver wheel 17 is stuck.
U.S. Pat. No. 5,636,557 to Ma issued on Jun. 10, 1997 discloses a ratchet type ring spanner including a ratchet wheel 20 mounted in a box end of a ring spanner. A spring 16 is mounted in a slanted manner for urging an arcuate toothed member 14 to engage with the ratchet wheel 20. A stop member 15 is utilized to provide a support for positioning the spring 16. Thus, there is no need to drill a hole in the web area of the ring spanner for installing the spring. Nevertheless, the stop member 15 results in a difficult assembly procedure. In addition, the arcuate toothed member 14 has a long travel and thus tends to be stuck and requires a larger head for receiving the arcuate toothed member 14.
FIG. 9 of the drawings illustrates a ratcheting tool including a ratchet wheel 1' mounted in a box end thereof. A spring 3' is mounted in a cavity 4' in the web area of the tool for urging a pawl 2' to engage with the ratchet wheel 1'. Nevertheless, installation of and positioning for the spring 3' are big problems such that the spring 3' tends to disengage from the pawl 2'. The pawl 2' has a long travel and thus tends to be stuck during its return travel.
FIG. 10 of the drawings illustrates a ratcheting tool 11' with a ratchet wheel 7' mounted in a head thereof for engaging with a socket 8'. A hole 9' is defined in the ratchet wheel 7' for receiving a positioning member 5' with a dome head. A spring 6' is mounted in the hole 9' for biasing the dome head of the positioning member 5' outward to engage with one of a number of arcuate recesses 10' in an outer periphery of the socket 8'. It is, however, found that the ratchet wrench includes too many components and thus is troublesome to assemble. In addition, the driving torque of this ratchet wrench is relatively low, as the positioning effect between the dome head of the positioning member 5' and the arcuate recess 10' is poor.
FIGS. 11 and 12 of the drawings illustrate a ratcheting tool 12' including a number of teeth 13' in an inner periphery of a box end thereof. A ratchet wheel 14' is mounted in the box end of the ratcheting tool 12' and includes a number of annularly spaced grooves 15' in an outer periphery thereof. A positioning member 16' is secured in each groove 15' and located between the teeth 13' in the box end and the ratchet wheel 14', thereby providing an engaging effect. Nevertheless, the positioning member 16' is too small and thus provides poor driving torque. In addition, assembly for this ratchet wheel is troublesome, as it has too many components.
FIG. 13 of the drawings illustrates a ratcheting tool 17' including a ratchet wheel 18' mounted in a box end thereof. A pawl 19' is mounted in a cavity 21' in a web area of the tool 17' and biased by a spring 20' to engage with the ratchet wheel 18'. The pawl 19' includes a notch 22' for receiving an end of the spring 20'. Nevertheless, it is not easy to secure the spring 20' in the cavity 21'. As a result, the spring 20' tends to disengage from the pawl 19' and thus adversely affects the ratcheting function. The driving torque provided by the ratcheting tool is accordingly low. In addition, the spring merely provides a radial force for biasing the pawl 19' to engage with the ratchet wheel 18', yet no horizontal force is imparted to the pawl 19' and thus fails to provide the function of ratcheting in a single direction.
FIGS. 14 and 15 of the drawings illustrate a reversible ring spanner including a ratchet wheel 24' mounted in a box end 23' thereof. A spring 27' is mounted in a cavity 26' in a web area of the ring spanner for biasing a pawl 25' to engage with the ratchet wheel 24'. It is found that the pawl 25' with a single tooth is not capable of providing the required retaining effect. The ratchet wheel tends to be stuck. The driving torque of the spanner is poor.
In conclusion, the above-mentioned conventional ratcheting tools fail to provide high torque operation, as the pawl merely engages with the ratchet wheel by at best three teeth. If the teeth number of the pawl is increased, the head of the ratcheting tool has to be enlarged to accommodate the pawl and thus is difficult to be used in a limited space. In addition, free rotation of the ratcheting tool during ratcheting is too large (larger than the theoretic value of 5.degree.), due to the long travel of the pawl.
The present invention is intended to provide an improved gear wheel/pawl engagement for a ratcheting tool that mitigates and/or obviates the above problems.